%% process_plot_ex_scalar
function process_plot_ex_scalar(pde, func_f, varargin)
[x, y] = meshgrid(linspace(pde.domain(1), pde.domain(2), 30), ...
    linspace(pde.domain(3), pde.domain(4), 30));
if isempty(varargin)
    exa = func_f(x,y);
else
    exa = func_f(x,y,varargin{1});
end
figure("WindowStyle", "docked");
surface(x,y,exa);
colorbar;
xlabel("x");
ylabel("y");
zlabel("analysis");
axis("tight", "equal");
view(-45, 60);
end